This invention relates to a method and apparatus for temperature control within a building. More specifically, the invention relates to a method and apparatus for concurrently controlling the temperature of many spaces within a building.
By way of background, most residential and many small commercial buildings (those of under 50,000 square feet) have a single Heating, Ventilation and Air Conditioning (HVAC) system serving all of the spaces within a building. The HVAC system typically includes apparatus for heating a medium fluid, such as water or air, apparatus for cooling the fluid, and some sort of transmission system for sending the fluid to spaces requiring heating or cooling. Typically, the HVAC system had a single transmission system which served to heat or cool the spaces. The heating and cooling systems were not used at the same time.
Connected to the HVAC system was some sort of temperature sensor and control. One prior art temperature sensor and control apparatus was the thermostat. A thermostat would be placed at some location within the building thought to be representative of the temperature of the entire building. Usually the thermostat was set by an operator to operate either in a heating mode or a cooling mode. The operator also entered a desired temperature, or setpoint, into the thermostat. The thermostat thereafter determined whether the temperature of the space varied from the setpoint, and if so, turned on the HVAC system until the difference between the setpoint and the actual temperature was eliminated. This temperature control method had the obvious problem that no matter what site was picked for the thermostat, some portions of the building were invariably too warm, while others were too cold.
In an effort to address the variance among rooms, each room was provided with a thermostat connected to the HVAC system and to a medium fluid flow control means. If one space required heating or cooling, the thermostat would cause the HVAC system to direct the conditioned medium fluid into the requesting space.
An equivalent system was provided by having a temperature sensor in each room, each temperature sensor being connected to a controller. The controller was in turn connected to the HVAC system and the plural medium fluid flow control means. Note that as a further example, plural thermostats were connected to a single controller to provide the desired control.
A problem with these last three examples existed in that while one room was calling for heat, another room might have been calling for cooling. One scheme for dealing with this problem was to have the controller average all of the differences between the setpoints and the actual temperatures for the rooms. If the average had a first relationship to a preselected constant, the HVAC system would be in a heating mode, otherwise the HVAC system would be in a cooling mode. A problem with this method was that if an unimportant room, such as an unoccupied basement, had a large temperature differential requiring heating when an important room, such as an occupied living room, had a small temperature differential requiring cooling, the basements' large heating demand would cause the HVAC system into heating mode. This leads to occupant discomfort.
In an effort to overcome this problem, the controller was modified to accept a range of values from 0% to 100% for a cooling priority. By way of example, a building owner could set a cooling priority of 30% which would cause the HVAC system to operate in cooling mode if 30% of the monitored spaces called for cooling. Thus, in a house having 8 rooms, if one room required cooling, 12.5% of the rooms required cooling, but this did not exceed the 30% minimum required and therefore cooling did not occur. If three rooms were calling for cooling, 37.5% were now calling for cooling, and therefore the HVAC system operates in cooling mode. However, even with this system, rooms which were unimportant from a temperature standpoint to the occupants could still cause undesired operation of the HVAC system. In the current example, if the three spaces calling for cooling were the basement (unoccupied), guest bedroom (unoccupied) and guest bath (unoccupied) while the other rooms in the building were calling for heating, the occupants were experiencing temperature discomfort.
It is therefore an object of the present invention to try to give heating or cooling priority to rooms that the occupants have identified as important to their comfort.